1. Field of the Invention
The present invention relates to a sheet storage device for stacking sheets discharge from an outlet of an image forming apparatus in order or in a regular manner on a sheet discharge table.
2. Description of the Background Art
Conventionally, the following prior art techniques relating to a sheet discharge device of this type mentioned above are known:
(1) A construction having a fence member provided upright on a sheet discharge table and a shock absorber mounted on the discharged sheet receiving surface side of the fence member with a gap between the shock absorber member and the delivery sheet receiving surface. The upper end of the shock absorber is supported in a manner as to be vertically movable and the lower end is fixed to the fence member. This construction is disclosed, for example, in JP 11-217151. In this prior art technique, a plate-like shock absorber such as a sponge member is provided on the front side of the fence member (the upstream side with respect to the sheet transport direction). The lower end portion of the shock absorber is fixed to the fence member by adhesive or the like, the upper side thereof is curved into a concave shape, and the upper end portion is held with clearance by an engagement portion formed in the upper portion of the fence member. Therefore, a gap between the fence member and the shock absorber is formed. Since the upper end portion of the shock absorber is held with clearance by the engagement portion of the fence member, it can be vertically displaced. Thus, when discharged sheets are stacked on the discharge table and the upper end portion of the shock absorber is downwardly displaced, there is little reduction in the change of the amount of gap between the fence member and the shock absorber at the sheet colliding position, with the result that the impact at the time of sheet collision is absorbed.
(2) A technique for preventing a sheet from sneaking through a gap between the lower portion of the fence member and the upper surface of the sheet discharge table, in which a “leg” extends from the lower portion of the fence member and a groove is formed in the upper surface of the sheet discharge table, causing the lower portion of the fence member to cross the upper surface of the sheet discharge table.
In the prior art technique (1), the cushioning behavior caused when the discharged sheet collides with the fence member differs in accordance with the kind of sheet, image condition, environmental changes, and the like. In some cases, since the sheet collision energy is not absorbed, and the sheet is returned to the sheet discharging outlet. Further, depending on the environmental condition and due to the temperature dependence of the shock absorber, the elasticity of the shock absorber may be changed. When the upper end portion of the shock absorber is held with clearance by the engagement portion formed in the upper portion of the fence member, the collision energy cannot be absorbed by the shock absorber alone. Thus, after the sheet collides with the fence member, the rebound is rather large. As the result, it sometimes impossible to stack the sheets in order or in a regular manner on the sheet discharge table.
In the prior art technique (2), when the fence member is positioned as it is at the sheet receiving position, it causes an obstacle at the time of removing the sheets stacked on the sheet discharge table. Thus, a construction is proposed in which the fence member is supported on the main body portion of a sheet storage device by a pivotable cantilever support arm and, when the discharged sheet is taken on out of the sheet discharge table, this support arm is rotated to cause the fence member to retract from the sheet removal area. In this construction, when the “leg” extends from the lower portion of the fence member as stated above, the following problem occurs. That is, when the support arm is rotated to cause the fence member and the shock absorber to integrally retract from the sheet removal area and to set them to the original positions again, there may be a danger of the operator such that his hand is caught between the above-mentioned “leg” and the upper surface portion of the sheet discharge table so as to suffer injury. This might be avoided by providing a gap between the lower portion of the fence member and the upper surface of the sheet discharge table. That, however, would allow the sheet to sneak through the lower gap after the collision with the fence member.
Technologies relating to the present invention are also disclosed in, e.g., JP 8-20468 A.